Composite restoration materials have been in use for more than 2 decades as an aesthetic alternative to metal restorations in the posterior region, which bears a great deal of the masticatory load, with increasing frequency in recent years.1 The early clinical data on the posterior region, gathered in the early 1980s, was not encouraging, primarily due to insufficient mechanical properties. The low abrasion resistance of those composite materials led to loss of restoration contours. Fractures, marginal deterioration and leakage following polymerization shrinkage were further reasons for the limited lifespan of those restorations.2-5 Predominantly in recent years, these inadequacies have been greatly reduced through further developments in the materials of the composite and adhesive systems.6 Nevertheless, the negative effects of polymerisation shrinkage—such as poor marginal integrity, insufficient adherence to the cavity walls or cusp deflections—still represent the greatest problem in composite-based materials.7
Today, hybrid composites or hybrid composites modified with nanoparticles are the material of choice when using a direct restoration technique for the permanent treatment of larger primary carious lesions or the replacement of older, insufficient restorations in the posterior region. Prerequisites are the correct use of the matrix technique and adequate moisture control of the cavity.8 Composites are processed in the incremental layer technique, usually in single increments with a maximum layer thickness of 2 mm. The individual increments are in turn each polymerized separately, with exposure times of 10 to 40 seconds depending on the light intensity of the curing device and shade/translucency of the respective composite paste. Above all, in large posterior tooth cavities this can be a very time-consuming procedure that, for economic reasons, requires a corresponding fee to cover the costs. However, many users wish for an alternative to the complex, time-consuming multiple-layer technique, in order to be able to process composites in a shorter time and therefore more economically.9 In recent times several interesting innovations have become ready to market in respect of this.
Economical Processing of Composites in the Posterior Region
In recent years, the dental profession has introduced numerous highly aesthetic composite systems to the market. With correct application, these enable direct restorations to be achieved that are practically impossible to tell apart from the dental hard tissue and can compete with the aesthetics of ceramic inlay restorations. These restoration systems contain composite materials in a sufficient number of shades and different opacities or translucencies (eg, Filtek Supreme XTE [3M ESPE]; Ceram-X Duo [DENTSPLY DeTrey]; Enamel HFO [Micerium]; Esthet-X [DENTSPLY]; Venus [Heraeus Kulzer]; Premise [Kerr]; IPS Empress Direct [Ivoclar Vivadent]). Some of these composite systems comprise more than 30 different composite materials of different shades and translucency. It is therefore essential to have appropriate experience in the handling of these materials, which are processed in the layer technique using varying opacities and translucencies.10
|Before Image. Initial situation: old, insufficient composite restorations in the posterior maxillary region.||After Image. End result: the direct composite restorations blend in well to the surrounding hard dental tissue. The tooth shape and aesthetics were restored.|
Aside from the possibilities that highly aesthetic composites offer in the application of polychromatic multilayer techniques, there is also a great demand in the dental profession—in some cases under great economical pressure—for the most simple and quick and therefore economical to place composite materials for posterior teeth.6 The restorative material amalgam, which has been used successfully for decades, is now fundamentally no longer acceptable to many patients. Nowadays, patients predominantly demand metal free restorations in the treatment of posterior tooth defects. While many patients avoid amalgam, above all due to insecurity about potential side effects, but also due to a lack of aesthetics— and this is therefore also no longer offered by a significant number of dentists—the phenomenon that gold inlay restorations are also increasingly being refused can be traced back to patients’ increased awareness of dental health and their desire for tooth-colored restorations.11,12
For the treatment of lesions in the masticatory load-bearing posterior tooth area that do not yet require complete crowning, direct composite restorations, indirect composite inlays/onlays and ceramic inlays/onlays are available to the dentist as long-term, clinically successful alternatives. The indication spectrum for direct composites in posterior teeth has distinctly increased in recent years. Whilst previously mainly small to medium-sized cavities, preferably circumferentially limited by enamel, were treated with direct composites, the steady, continuous improvement in composite materials and related adhesive systems, combined with positive experience from numerous clinical trials, have resulted in the possibility to greatly increase these indications. Today, Class I and II defects, without explicit qualification of size, can be successfully treated with direct composite restorations, even including the replacement of individual cusps, and without the need for circumferential enamel limitation. However, especially in very extended defects, it should always be ascertained if individual cases would benefit more from indirect restorations (ceramic or gold inlay restorations), due to better stabilisation of weakened hard tissue, limited accessibility to the treatment area or expected problems in shaping the proximal contacts. If it is not possible to keep the treatment area clean, leading to a danger of contamination of the cavity site with blood, saliva, or sulcus fluid, an adhesive restoration should certainly be avoided.
Composite restorations have been shown to be highly successful in the treatment of posterior teeth.13 However, the basic rules for the adhesive technique must be adhered to in such cases. These include, for example, careful observance of the adhesive protocol, the increment technique with observance of the curing depth of the individual layer of the respective composite, sufficient light-polymerization and careful finishing and polishing.14 In general, adhesive restorations show a great deal of technique sensitivity. The same material often shows highly significant variation in the success achieved by different operators.15
The correct observation of the rules of the adhesive technique is extremely time consuming for the dentist. This must be reflected in economically calculated prices corresponding to the effort required. However, many nonprivately insured patients are simply financially unable to take on the corresponding additional costs. With this group of patients, dentists regularly find themselves in the following dilemma:
1. The patient does not want to opt for amalgam;
2. Glass ionomer cements (and derivatives), as well as other cement restoratives, are currently not suitable as permanent restorations due to an increased risk of fracture or wear in the areas affected by masticatory loads16-18;
3. The amount of the additional costs for multilayer direct composite restorations with dentine-adhesive fixation exceeds the patient’s budget; and
4. Crowning is not yet indicated, and would also be accompanied by extensive additional costs to the patient.
On the other hand, one cannot expect the dentist to set an economically absurd, low price for a high-quality, time-consuming types of restoration produced using not exactly inexpensive composites, which would result in the dentist making a financial loss at the end of the day. The basics of business economics must not be forgotten in this: The price of a treatment is made up of the materials used, the time taken and all costs connected with this, which include, among others, the cost of staff, property rental, depreciation, etc, plus energy and storage costs, and finally the clinician’s own salary. In order to treat patients who are only able to manage smaller private contributions, therapies must be available that show both reasonable clinical performance in the highly stressed posterior teeth, as well as being economically sensible for the dentist to deliver. Accordingly, the desire for restorative materials that are faster and easier to process and can therefore be offered at a lower price is totally understandable.19 Many practices have a patient structure that demands an economical treatment strategy with less demanding restoration types.12
Basic treatment in conservative dentistry would benefit from a material as an alternative to amalgam, whose limited sensitivity to application technique and clinical longevity would combine with the structurally stabilizing properties of the adhesive technique. The optical properties of such a material for posterior teeth are of less importance for patients, as long as the result is not metallic or cement-like and extremely opaque. In the author’s view, it is even of advantage if in comparison to the highly aesthetic composite restorations, which are much more laboriously applied using the polychromatic multilayer technique, a distinct difference can also be perceived by the patient.
A number of composite manufacturers have assimilated the demands of practitioners into their requirement specification for material development and are trying to simplify composite-based restoration techniques in the posterior region. For this so-called “fast-track” restoration technique, simplified bonding agents (usually single-step, self-conditioning adhesive systems) are used in combination with low-shrinkage, mechanically sufficiently stable composite materials that can be applied directly into the cavities.19,20
In general, the following factors, amongst others, can contribute to placing a light-curing composite restoration in posterior teeth faster and therefore more economically:
- Universal shade of the restorative material ⇒ Omission of the sometimes complicated shade selection (especially if the patient is potentially included in this procedure)
- More translucent shade of the composite ⇒ Greater curing depth per layer, meaning fewer increments
- Optimization of the light-curing composite’s initiator system ⇒ Shorter exposure times
- Low-shrinkage composite materials with minimal polymerization stress build-up ⇒ Greater layer thicknesses, meaning fewer increments
- Powerful polymerization lights ⇒ Shorter exposure times with high intensity
- Functional but efficient shaping of occlusal anatomy ⇒ Faster finishing and polishing procedure.
The “fast-track” composites should, with the best possible quality of restoration margins, be easy to handle21 and less sensitive to technique, and should additionally provide more economical processing techniques and thus save time in placement.22 As most of these composites are only supplied in one single shade, selection of the matching shade is also no longer required. Despite this, the use of these materials results in adequately aesthetically pleasing results, especially in comparison with amalgam and glass ionomer cements. For the purpose of a comprehensive “fast-track” concept, these composites are normally used in combination with self-conditioning bonding agent systems, without the use of separate enamel-dentin etching.
The material properties of these composites, optimized to be economical, are comparable to conventional light-curing composites.23 Data from clinical trials shows good intraoral performance.24-26
The low-viscosity, flowable composite x-tra base (filler content: 75% by weight) (VOCO America) exhibits reduced shrinkage on a traditional methacrylate basis. It is indicated for the bulk-filling technique, in order to establish a maximally 4.0-mm thick restoration base (“cavity lining”) in Class I and II composite restorations. In a subsequent step after curing, this increment must be covered in the region of the occlusal anatomy by another capping layer of a methacrylate-based hybrid composite at least 2 mm in thickness and suitable for posterior teeth, such as the nanoparticle-modified hybrid composite GrandioSO (VOCO America). Alternatively, x-tra base can also be applied in the first thin layer as a cavity liner in Class I and II cavities. X-tra base is supplied in the shades Universal and A2. Depending on the light output of the polymerization device and the selected shade, the polymerization time is: 10 seconds for the “Universal” shade, if the light output is at least 500 mW/cm2; 20 seconds for the shade “A2,” if the light output is at least 800 mW/cm2; otherwise 40 seconds (500 to 800 mW/cm2).
The following clinical case is a stage-by-stage representation of the replacement of 3 old, insufficient composite maxillary posterior tooth restorations with the composite combination of x-tra base and GrandioSO in a clinical step-by-step series, as part of a clinical “fast-track” procedure.
Diagnosis and Treatment Planning
A patient complained of osmotic or thermic irritation in her first quadrant posterior teeth, which contained old composite restorations with unsealed margins. During the clinical inspection, the teeth reacted sensitively in the cold test and showed no negative reaction to the percussion test. In consultation with the patient it was decided to replace the insufficient composite restorations. After an explanation of the possible treatment alternatives, the patient decided on composite resin restorations.
Treatment started by thoroughly cleaning the affected teeth in the first quadrant of external deposits using a fluoridefree prophylaxis paste and a rubber cup (Before Image). After careful removal of the insufficient composite restorations, while conserving the remaining hard tissue, the teeth were excavated, the cavities completely prepared and finished with a fine diamond bur. Figure 1 shows the situation after the application of the rubber dam. The rubber dam separates the operation site from the oral cavity, facilitates clean and effective work and guarantees that the working area remains clean of contaminating substances such as blood, sulcus fluid, and saliva. Contamination of the enamel and dentine would result in distinctly poorer adhesion of the composite to the dental hard tissue and endanger the long-term success of a restoration with optimal marginal integrity. Additionally, the rubber dam protects the patient from irritating substances such as the adhesive system. The rubber dam is thus an essential aid in ensuring quality and facilitating work in the adhesive technique. The minimal effort required in applying the rubber dam is also compensated by avoiding the changing of cotton rolls and the patient’s frequent requests and need for rinsing.
Initially, both premolars were restored in parallel. Metal matrices were anchored with wooden wedges in order to delimit each of the triple surface MOD cavities (Figure 2). In order to optimize the contours, the matrices were then also carefully molded with a hand-instrument (cold-forming). The formation of a physiologically contoured proximal surface with tight contact to neighboring teeth still represents a challenge when using composites. In contrast to amalgam, composites show a certain viscoelastic recovery from distortion, which is often seen as undesirable by the user and which complicates the adaptation of matrices to the neighbouring tooth by packing pressure.27,28
|Figure 1. Situation after removal of the old restorations, excavation, preparation, and application of the rubber dam.||Figure 2. Demarcation of the cavities in both premolars with metal matricies and wooden wedges.|
|Figure 3. Adhesive pretreatment of the hard tissue with the self-etching adhesive (Futurabond DC [VOCO America]).||Figure 4. Light-curing of the bonding agent for 10 seconds.|
|Figure 5. Check for a shiny cavity surface, evenly covered with adhesive.||Figure 6. Determination of the maximum cavity depth with a scaled periodontal probe.|
|Figure 7. Application of x-tra base composite (VOCO America), using shade “Universal,” into the cavities in a 4.0 mm layer using the bulk technique.||Figure 8. Polymerization (light intensity> 800 mW/cm²) of x-tra base composite (shade Universal) for 10 seconds.|
|Figure 9. Cavities, evenly filled with x-tra base (self-leveling flowing behavior), with around 2 mm of distance for the shaping of the occlusal anatomy, using a composite suitable for posterior teeth, still available.||Figure 10. Application of the methacrylate-based, posterior tooth-suitable composite (GrandioSO [VOCO America]) for building up the occlusal surface.|
The self-conditioning adhesive Futurabond DC (VOCO America) was selected for bonding. The self-etching adhesive was applied and distributed generously in the area of the cavities using a microbrush (Figure 3). It must be ensured that all cavity areas are sufficiently covered by the adhesive. After at least 20 seconds of carefully massaging the adhesive into the hard dental tissue, the solvent was carefully evaporated with oil-free compressed air from the bonding agent, which was subsequently cured for 10 seconds with a polymerization light (Figure 4). The result was a shiny cavity surface, evenly covered with adhesive (Figure 5). This should be carefully checked, as any areas of cavity that appear dull are an indication that insufficient amount of adhesive has been applied to those sites. In the worst case, this could result in reduced bonding of the restoration in these areas and, at the same time, in reduced dentine sealing, which may lead to postoperative sensitivity. If such areas are found in the visual inspection, additional bonding agent is again selectively applied to them.
The deepest areas of the cavities were measured with a scaled periodontal probe, as x-tra base can be applied in the bulk technique in layer thicknesses of up to 4 mm (Figure 6). However, approximately 2 mm must remain in the area of the occlusal anatomy for completion of the restoration with a capping layer using a methacrylate-based composite suitable for posterior teeth.
The composite x-tra base, in the translucent Universal shade, was applied in the bulk technique in a layer thickness of 4 mm, injecting directly into both cavities from the nondripping NDT syringe, and starting at the deepest area of the defect (Figure 7). In order to avoid the inclusion of air bubbles, the thin metal tip of the syringe should constantly remain submerged in the material flowing out. Within a few seconds, the flowability of the material leads to self-leveling of the composite layer. Any visible air bubbles in the material should be eliminated with a probe tip. The translucent composite x-tra base was cured with a high-performance polymerization light (light intensity > 800 mW/cm2) for 10 seconds per cavity (Figure 8). Figure 9 shows the cavities, evenly filled with x-tra base, with around 2 mm of occlusal remaining distance still available for the shaping of the occlusal anatomy, using a capping layer of methacrylate-based composite suitable for posterior teeth.
The occlusal surfaces of both premolars were built up in one further step with the composite GrandioSO in shade A2 (Figure 10), completing the restorations (Figure 11). After 10 seconds of polymerization (light intensity > 800 mW/cm2), the restorations were checked for imperfections and the metal matrices were removed. The composite restoration in the second premolar was finished and polished in the distal region that would later not be accessible anymore, before the restoration of the first molar was started.
The triple surface MOD cavity in the first molar was then delimited with a metal matrix, which was anchored with wooden wedges (Figure 12) After adhesive pretreatment with the self-conditioning adhesive Futurabond DC (Figures 13 and 14), the composite x-tra base in Universal shade was applied directly into the cavity in the bulk technique with a layer thickness of 4 mm (Figure 15). It was again ensured that there was still 2 mm of occlusal room for the covering layer. After at least 10 seconds of polymerization (Figure 16), x-tra base was covered with a layer of GrandioSO (shade A2) (Figure 17). After a final polymerization cycle (Figure 18) the matrix was removed (Figure 19). Figure 20 shows all 3 restorations before finishing.
|Figure 11. Completed restorations after light-curing, before finishing.||Figure 12. Demarcation of the cavity in the first molar with a metal matrix and wooden wedges.|
|Figure 13. Situation after the adhesive pretreatment of the hard tissue with the self-etching adhesive (Futurabond DC).||Figure 14. Light-curing of the bonding agent for 10 seconds.|
|Figure 15. The x-tra base composite (shade Universal) is applied into the cavity in a 4-mm layer using the bulk technique.||Figure 16. Polymerization (light intensity > 800 mW/cm²) of x-tra base composite (shade Universal) for 10 seconds.|
|Figure 17. Situation after application of the methacrylate-based, posterior tooth-suitable composite (GrandioSO) (shade A2) for building up the occlusal surface.||Figure 18. Polymerization (light intensity > 800 mW/cm²) or 10 seconds.|
|Figure 19. Situation after removal of the matrix system.||Figure 20. Final check of all restorations before removal of the rubber dam.|
Once the rubber dam was removed, the fissure relief and fossae were finished with a pear-shaped finishing diamond bur. In the next step of the standard finishing sequence, a point-shaped fine-grit diamond was used to finish the convexity of the cusps and triangular ridges. After the elimination of occlusal interferences and adjustment of the static and dynamic occlusion, the accessible proximal areas were contoured and prepolished with abrasive disks. The use of diamond-impregnated composite polishers (Dimanto [VOCO America]) achieved a satin matte, lustrous finish on the surface of the restorations. The subsequent high-gloss polishing was carried out using the same Dimanto polishers with reduced pressure and optimized the luster of the restoration material. The After Image shows the completed direct restorations with the composite combination x-tra base and GrandioSO in maxillary posterior teeth, reconstructing the original tooth shapes with anatomically functional occlusal surfaces and physiologically formed approximal contacts. Finally, a foam pellet was used to apply the fluoride varnish Bifluorid 12 (VOCO) to the affected teeth.
The importance of direct composite-based restorative materials will continue to increase in the future. These are scientifically proven, high-quality permanent restorations for the masticatory load-bearing posterior region, whose reliability has been documented in literature. The results of a comprehensive review have shown that the annual failure rates are not statistically different to amalgam restorations.13 Minimally invasive treatment protocols, in combination with the ability to detect carious lesions even earlier, also have a positive effect on the longevity of such restorations. However, in order to ensure a high-quality direct composite restoration with good marginal adaptation, a careful matrix technique (in cavities with approximal involvement), an effective adhesive system, the correct processing of the restorative material and the achievement of a sufficient level of polymerization of the composite continue to be basic prerequisites.
The increasing financial pressure in the healthcare system and, in many cases, the lacking financial means of patients with regard to additional payments adequate to services, require, aside from time-consuming high-end restorations, a simpler, faster to complete and therefore more economical basic treatment. However, composite-based basic treatment will not manage completely without private contributions (persons insured via statutory health insurance scheme). The time advantage associated with the “fast-track” technique can however reduce these accordingly.
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Dr. Manhart is professor, department of restorative dentistry, Dental School of LMU-University in Munich, Germany. He offers seminars and practical workshops in aesthetic restorative dentistry, such as direct composite restorations, all-ceramic restoration, postendodontic treatment (aesthetic root posts), management of worn dentition, and treatment planning in aesthetic dentistry. He can be reached at email@example.com.
Disclosure: Dr. Manhart reports no disclosures.